Several weeks ago, the hostnames I had assigned to the Windows, OS/2, Linux, and Mac OSX machines started being replaced by names of the form hostxx-null.null.bellsouth.net where "xx:" is 192.168.1.xx. Bellsouth.net is my DSL ISP.

Every once in a while, the original hostnames of some machines make a bried reappearence. The Cayman DSL modem/router/hub (the DCHP server for my LAN) has never displayed anything but the names I assigned. I don't remember whether this strangeness started before or after, but I have assigned separate hostnames to NICs in linux boxes that have two.

Can anyone suggest what might be going on and how to fix it?